Friday, 22 May 2015

Oslo workshop – Day 5

It's day 5 at the Oslo gamma strength workshop.  I've learnt quite a lot – particularly about how rich the data is from a wide range of experiments, and also how it is difficult to reconcile the interpretation of different experiments using different methods (such as those that excite nuclei with gamma rays vs those that use neutrons).  My talk is coming up later today, and I hope to get some good questions and suggestions for what I might calculate.

As much as I have been enjoying the conference, if I had been a bit quicker to notice, I'd have skipped one of the sessions on Wednesday because there were taking place, in the next building, the Abel lectures from this year's Abel prize.  The Abel prize, named after Norwegian mathematician Niels Henrik Abel, was set up in response to the Nobel prize not featuring a mathematics prize.  It's a prestigious thing, and the award this year went to John Nash Jr and Louis Nirenberg, both of whom were speaking on Wednesday, followed by longer talks about their work and legacy.  Quite an opportunity missed by me to go and see them!

Being at the University of Oslo, too, reminds me about gnus -- a computer program which runs under that operating system (and text editor) known as Emacs.  I used to use gnus as a newsgroup reader, and as an email program.  It is a brilliant program and could do all sorts of neat things, helped by the fact that it was extendable by users who were prepared to do a bit of emacs-lisp programming.  I was, and I even contributed a couple of patches to fix bugs in beta versions of the program.  As a result, my name can be found on every unix (including Apple Mac) computer, in the file containing the list of contributors to the gnus part of emacs.

Yesterday was the conference outing and dinner.  The outing was to Oscarshall, a royal palace set in a peninsula a short walk from the city centre.  The picture above does not do justice to the pretty meadow full of dandelions that we walked past on the way there.  The dinner was very fancy, and very tasty.  The Paleo Brasserie catered for us very well, and in particular gave me an excellent vegetarian meal.  The dessert was white chocolate with dill ice cream.  It's safe to say that I have never had dill ice cream before.

Update: The day after writing this post, John Nash travelled back from Oslo to New Jersey, and died in a car crash on his way home from the airport.

Wednesday, 20 May 2015

The Oslo Method

I'm in Oslo this week for a workshop on gamma–ray strength and level density -- essentially the study of how strongly nuclei respond to being hit by gamma rays, as a function of the gamma ray energy, and what you can tell about nuclear structure through it.  They are experts on the topic here in Oslo, performing experiments with their cyclotron and deducing the gamma strength and level density using the Oslo Method, which sounds like a Cold War thriller. 

I came because I've been involved a bit in calculating strength functions, so I've come to advertise my method to the community.  The code I use to do it has been published and is available for anyone to use, so hopefully my talk will spur some applications of the code.  I also came for the excellent buffet, presented on Monday evening, as shown in the picture.

I started the #oslogamma hashtag on Twitter which has been picked up by a few other participants, so if you are reading this post in the week that I posted it, then you can follow a bit of live-tweeting.

Thursday, 30 April 2015

Bricks and mortar

One thing that readers in the UK will have probably noticed is that there is a general election next week.  Science has not been a particular topic in the election campaigns of hopeful MPs or their parties, and neither would one particularly expect it to be.  One slightly tangential way in which political issues comes up in nuclear physics is in the cost of accommodation -- something that has come up somewhat in the pre-election debates.  

Universities in the UK pay salaries on a national scale, so that those in one part of the country earn the same as those in another.  Equal pay for equal work is sensible enough, but when living in one part of the country costs twice as much as another part, then a policy of equal quality of life would seem more reasonable.  Here, in the South East of England, housing is particularly expensive.  It's a problem when we want to attract people to the University.  If things don't change, the obvious answer seems to me to be that we should just stop having public services in the south-east.  If people want to have children going to school, they should move up north.  If they get cancer they can move up north for treatment, and so on.  We even have a new political party in Guildford (the Guildford Greenbelt Group) who have determined to stop teachers and nurses moving here, because Guildford is not for such as them.  

Sometimes I am surprised that the University does not campaign more to increase the pay of staff.  Presumably they want to attract staff here, yet, they argue that pay rises should be as small as possible.  The picture attached is a 3 bed semi-detached house currently on sale quite close to the Univeristy.  The cost is around 10 times a professorial salary, which is already quite a high salary.  

Let's move all schools, universities, hospitals, doctors, refuse removal, and other such services to the north, until the situation improves.  Surely, that'd be okay?

update on 3rd May: There were so many other pertinent things that I should have included in this post, like the fact that house price inflation is running at around 10% -- nothing like the real inflation rate.  This is mostly caused by a constant stream of ways in which successive conservative governments (with a small "c" -- whether Labour or Conservative in manifestation) do everything they can to prop up house prices, as if that's a desirable thing.  Here's a nice post post that I read today by Alex Grant on the property situation in the UK, with some insight from his time as a councillor in London.

Tuesday, 28 April 2015

A lot of beta decay

Working where I do -- in a nuclear physics research group that is one of the largest in the UK -- we get a pretty good programme of visitor seminars.  As a rule, it's one per week, with sundry other visitors speaking as and when they happen to be here, or passing.  In fact, quite a few visitors make use of the fact that we are near London and pop down to catch up and give a talk when in transit.

Today we had a talk from Giuseppe Lorusso.  He works at NPL, which is almost certainly our closest neighbour in the world of nuclear physics, up the road in Teddington.  His appointment there comes in conjunction with a closer collaboration between our two institutions, which includes a couple of our academics now having joint Surrey–NPL appointments.  

Giuseppe talked mainly about his work at RIKEN, where I visited last week.  In particular, it was concerned with an impressive set of new measurements of beta–decay lifetimes of neutron–rich isotopes, many of which had not been measured before, with some which had, but with poorer accuracy.  He gave a nice motivation in terms of the generation of elements heavier than iron.  While all elements heavier than lithium (element #3) are made in stars, elements heavier than iron (e.g. gold, lead, uranium, tin, xenon, and a whole host of others) are made only in particular stellar processes.  They have to involve nuclear reactions involving neutron capture.  It is clear from the current abundances of elements that at least some of these processes have to be really fast -- with lots of neutron captures happening in the order of seconds or minutes with subsequent beta decay leading to the isotopes we see now.  It used to be a matter of faith that core–collapse supernovae were the events that gave rise to this rapid neutron–capture process (the "r–process"), but that no longer seems certain, since the models of such events don't seem to have the right neutron fluxes or temperatures.   Current best guesses include high–magnetic–field spinning supernovae, or merging neutron stars, though they each have their problems.

In any case, to understand what goes on in these processes, we need to know the decay lifetimes of nuclei all over this region.  The difficulty is that these very neutron–rich isotopes only exist in nature during these stellar events.  We can make them artificially, but only now with the facilities on offer today have we been able to get close.  In particular, at RIKEN, where a beam of uranium–238 nuclei is collided with a beryllium target, almost anything lighter than uranium can be generated.  One of the things that makes RIKEN special is its ability to separate out all the results of the reactions in a clean way.  Giuseppe's talk showed a wonderful particle identification plot showing the large number of isotopes generated in the experiments;  tens of which had never had their beta–decay half lives measured.  What did the new data tell us about the stellar processes?  The main conclusion seemed to be that (unlike in very light nuclei) the "magic numbers" representing very stable nuclei seem to be pretty robust, lasting well in to the neutron rich region.  This is in contrast to some theoretical ideas suggesting that the nuclear spin–orbit interaction would become weaker here.  

Giuseppe is pictured above, just as he was talking about neutron star mergers.

Monday, 20 April 2015

Big in Japan


Following a trip to see a student on placement at the University of Massachusetts last week, I'm now in Japan seeing another one (see photo), who is based at the RIBF (Radioactive Ion Beam Facility) in RIKEN, just outside Tokyo.  Lily is working on a new storage ring which will be used for precision mass measurements of exotic isotopes that will hopefully shed light on the r–process which takes place in stellar explosions and is responsible for creating heavy nuclei that we find on Earth today.  The intermediary nuclei in these nuclear reactions are very neutron rich and unstable, and the ones created in the stellar environments decayed very shortly after their creation.  The facility at RIKEN is currently unique in the world in its ability to create such neutron-rich isotopes

I had a guided tour of the lab this morning by Lily and her supervisor.  It's a lot cleaner and shinier than most other labs I have been to (with the possible exception of the NIF in the US), but I have been assured that it was just because the bits I was seeing were so new, and not quite in operation yet.  The storage ring will be tested and ready for use during the year, so it should be a good year to be here on placement.  Ironically, this nuclear physics lab cannot run for as much of the year as it used to due to the increase in electricity costs following the 2011 earthquake and tsunami and the damage at the Fukushima nuclear power plant.  Japan has shut down all its other nuclear reactors, which used to provide around 30% of the country's electricity.  

Thursday, 16 April 2015

Swatting the Fly in the Cathedral

I've just finished my visit to UMass Lowell, where the Surrey student on placement is getting on very well.  The group who have kindly paid for him to come out and work with them are pleased with how he is doing, and I was impressed with how far he'd got in understanding how germanium detectors and the corresponding electronics work.  Hell, I still thought germanium detectors detect germanium, and Tom put me straight.  

I gave a seminar to the Physics Department at Lowell today.  I had initially given it a rather pedestrian title – I can't remember what now, but my host suggested I spice it up a bit, and I went for "Swatting the Fly in the Cathedral," referring to the title of a popular science book about nuclear physics, in which the fly in the cathedral is an analogy in terms of size of a nucleus in an atom; i.e. really, an atom is a lot of empty space.

I think the seminar went okay.  Always hard to tell.  There was a a great bunch of Emeritus staff present, including one from the UK who had left for the States long ago, and another who had been at Sussex in years past.  We had a good chat over lunch, talking about mutual acquaintances, and memories of places in common.  That generation of academic – especially in nuclear physics and in the US really takes me back to my time at Oak Ridge, where there were still those who could talk about the early days of nuclear physics. 

Now I'm waiting at Boston airport to fly home.  I leave at 10pm local time here, and arrive at 10am local time in England.  Then I will make my way to be a human in the cathedral in Guildford, where our graduation ceremonies take place.  There'll be two of my recent PhD students there, and I hope to be fully awake through the whole thing.

Monday, 13 April 2015

U Mass


I'm at UMass Lowell for a few days this week, mainly to visit one of our MPhys students who is on placement here for his Research Year.  I had Sunday to myself, and contemplated doing tourist things in Boston, but decided in the end to see what Lowell had to offer.  It's an old mill town, and there is lots of related heritage.  I wandered round the town, and it was a lovely day.  The first warm day of the year so far, apparently.  I went to Kerouac Square, in honour of Jack Kerouac who was born in the town (though famously wandered away from it).  I went to the American Textile History Museum, and I tried to find somewhere to eat at a Sunday lunchtime.  Some pictures from my day are at the top of the post.

There are no doubt a lot of reasons to go to visit Boston itself.  To me, it famous for being the birthplace of some of my favourite bands from the late 80s/early 90s.  I feel like I shouldn't let a visit to UMass go by without posting the Pixies' song UMass.  This version was recorded live at the Tsongas Arena, here on the campus in Lowell.  It's from the Pixies' last album, in 1991, before their long hiatus (their follow-up album was released last year), and is not really one of their better songs, in common with the whole album... but it's certainly relevant for me sitting here in UMass today.